The present invention relates to a thread stitching machine for processing signatures into book blocks, wherein the thread stitching machine includes a transport system for the signatures and a downstream installed stitching station, and the transport system includes a transporting section on which the signatures are positioned straddling and for being supplied to the stitching station. The invention additionally relates to a method for operating such a thread stitching machine.
Conventional thread stitching machines can only be set up for a single format each time, wherein this is achieved with the aid of mechanical connections, for example the use of gear clutches and magnetic brakes during the setup for the production. However, this system cannot be adjusted flexibly during the course of the production, thereby causing problems when book blocks are composed of different-size signatures, also called print sheets, for example if they are designed in this way as an art print or for other design reasons.
In particular if the signatures are to be transported with the bottom side and retrieved with the top side or if they are to be transported and transferred with the top side, this is either not possible or only with restrictions as a result of the inflexible format adjustment, wherein this results in a reduction of the production speed, a machine stop, or having to continually deposit the signatures by hand.
The placement of signatures of different sizes by hand onto a stitching stack, as is the practice at the present time, involves dangerous safety-technical sequences which are no longer tolerated by the authorities in charge of safety, owing to the fact that the machine operator is in great danger of sustaining serious injury to his/her fingers.
For safety-technical reasons alone, the use of machines with an auxiliary saddle support would therefore be preferable. The disadvantage of such machines is the constantly repeating, monotonous movement sequence for the operator when depositing the individual, manually opened signatures. The danger of mixing up signatures furthermore exists, which should not be overlooked and which can lead to a rejection rate which cannot be ignored. However, manually depositing signatures with different formats onto the auxiliary saddle is possible only if the conveying chain has no fixed position.
A different option of producing a book of this type, provided with below-standard format inserts, is to divide this book into several parts and to subsequently combine the thread-stitched parts. With this type of process, all full-format signatures which are also called standard format signatures are initially stitched together, up to the point until a below-standard format signature is reached. Subsequently, all standard format signatures that follow below-standard format signatures are processed and finally, the below-standard format signatures are stitched together. In the end, a book with at least three thread-stitched partial book blocks is produced which can subsequently be adhesive-bound in the correct sequence.
Owing to the increased demand for books of this type, for which at least one section differs for design reasons from the remaining part of the book, the standard sequences used with thread stitching machines known from the prior art are no longer sufficient since a reliable economic production can no longer be realized with any of the known techniques.
In this context and in view of the known prior art, we additionally refer to the European patent document EP 2 184 177 A1 which describes a machine for the thread stitching of folded printed products. According to this document, the individual printed products are stitched along the fold with a stitching or sewing machine and are then sewn together along the back provided with the fold, so as to form a book block, wherein the printed products are supplied to the stitching station while positioned individually and straddling on a pivoting saddle. This document forms an integral component of the specification for the present application and its disclosure is incorporated herein by reference.